Method for producing a fibre concrete slab for paving low-traffic roads, concrete slab, and method for paving low-traffic roads

ABSTRACT

The invention relates to a method for paving low-traffic roads or paths with a paving slab that is cast in situ and has a width Dx narrower than the smaller value of D1 and D2, wherein D1 is the free distance between the front wheels of a standard haulage truck and D2 is the distance separating the wheels of the rear-wheel train, being the length of the paving slab Lx shorter than the value of the length L of the free distance between the front axle and the first rear axle of the wheel train of the standard haulage truck, such that the dimensions Dx and Lx mean that a single wheel or, alternatively, a single wheel train of the standard truck is always supported by the paving slab, touching same. The method comprises the steps of: providing for paving either a low-traffic road which has neither asphalt or concrete paving, or a low-traffic path; evening out and levelling the road or path to be paved; determining the width and length of the paving slab and establishing the thickness thereof in accordance with the amount of traffic and the traffic load, the bearing capacity of the natural ground, the strength of the concrete, the residual strength thereof and the climate, such that the thickness is between 5 and 15 cm; determining the amount of fiber required for a required design residual strength of between 10% and 50% of the maximum strength of the concrete; and preparing the mixture of concrete and fibers which are selected from steel, glass, polypropylene, carbon or another structural fiber for concrete. In addition, the method comprises pouring the mixture of fiber concrete directly onto the road or path to be paved according to

FIELD OF THE INVENTION

The invention relates to slab of concrete with fiber for paving roads oflow traffic or similar, which presents a smaller thickness andpredetermined width and length dimensions.

The present invention further relates to the method of manufacturingfiber slab for paving roads of low traffic, and with the method forpaving roads of low traffic.

BACKGROUND OF THE INVENTION

The unpaved roads are highly polluting, since the movement of vehicleson them, generates large amounts of dust; therefore, it is recommendedthat they be paved with gravel in order to make them more passable,since it is possible to eliminate the dust production. However, ongravel roads vehicles have less stability and adhesion, and to transiton unpaved roads is recommended that vehicles circulate at moderatespeed and have their tires properly inflated, so that the stones do notbreak the tread.

In addition to this, the cost of maintenance of these roads is veryhigh, especially in those which circulate trucks, since the surface ofboulders based on granular materials tends to decompact with the trafficof vehicles, eliminating the good quality material of the surface andproducing calamine and pits on the surface.

The problems identified in the unpaved roads generate the need to pavethe road with other materials or to perform some treatment to the rippedsurface to improve transitability of vehicles. Generally, the solutionin these cases is the asphalting of the road. Furthermore, there is thepossibility of concrete paving the road but this solution although moredurable, can be more expensive than the process of asphalting. Inaddition to the above described, in both cases it is necessary to removea portion of the existing road and to replace it with a good qualitygranular paving, to obtain both the structural capacity and the existingsoil erosion; This not only increases the cost of the solutions, but itis also not-sustainable because it requires removing material out of theroad.

Additionally, when choosing the most suitable material for paving, inthe case of concrete, the dimensions of the slabs used in paving roadsmust be taken into consideration. Usually, the concrete slabs for pavingroads have dimensions which usually have the width of a via, usually3.500 mm, having a length of 3.000 to 6.000 mm. To bear the burden ofheavy trucks that generate the greatest efforts and stresses to whichthe slabs are subjected, it is necessary to worry about the slabthickness, since the thickness is important to prevent cracking of theslabs. Moreover, some of the slabs designs of the prior art have armor,mesh or ironworks in their structure in order to ensure the durabilityof the slab, but such an aggregate results in a considerable increase inthe cost of slab design. Moreover, in the state of the art concrete withfibers are developed which consist of concrete made from cementcontaining fine and coarse aggregate, and staple fibers, where thefibers may be natural or artificial and have the function of reinforcingthe cement mass, increasing the fatigue resistance and thus slowing thegrowth of cracks, thereby increasing ductility to transmit the forcethrough the cracked section. Moreover, the reinforcing fibers improvethe impact resistance, and allow contraction joints distance byhydraulic shrinkage. The fibers most used for this type of concrete arefibers of steel, glass, polypropylene, carbon and aramide, and ingeneral are called structural fibers.

In fiber concretes, once produced the first crack of the concretematrix, the tensile stress should be distributed on the fibers presentin the cracking zone, and these must hold together the edges of thecrack at the lowest possible width. By continuing to increase thetensile stress, the concrete begins to deform, this is why it is veryrelevant for the behavior of residual fibers.

This effect in conjunction with the support provided by the soilgenerates a different pattern of cracks in the concrete without fiber,distributing efforts and reducing fatigue in the crack tip, greatlyincreasing the capacity of load cycles and, therefore, the duration.

For the Determination of the Residual Strength:

The residual strength although is not a real property but an engineeringeffort, calculated based on the properties of the section, according tothe theory of engineering simple bending for linear and nonlinearelastic materials (seamless), in practical terms is a material's abilityto continue taking loads once cracked.

The addition of fiber increases the flexural strength of a slab, a factthat is demonstrated in the testing of supported on floor slabs, but isnot clearly reflected when testing of beam in the air are performed.

The current pavement designs are directly linked to the flexuralstrength of concrete (MOR) and do not take into account the residualstrength that the fibers provide. Therefore, the beam tests do notreflect the actual contribution of the fibers in the concrete in thepavement design. Consequently, for testing of beam, the design woulddeliver the same thickness of a concrete pavement with fibers to onewithout fibers.

By testing, a series of load-deformation points is obtained, asillustrated (ASTM 1609) (FIG. 4).

In FIG. 4., P1 represents the strength of the concrete, that is to say,the maximum load that resists the said concrete (MOR); P150.0.75corresponds to the residual strength, that is to say, the load that theconcrete resists to deformation of S/600, where S is the separationbetween supports (mm); and P150.3.0 corresponds to the residualresistance, that is, a load that the concrete resists to deformationS/150.

With the above described data we can calculate the maximum voltage forany value of P with the following equation:

$f = \frac{PL}{{bd}^{2}}$

where:

F=Tension (MPa)

P=Load (N)

L=Separation between supports (mm)

b=average width of test tube in the crack (mm)

d=average height of test tube in the crack (mm)

Following the procedure of ASTM 1609 standard, if the fracture occurs inthe middle third, the equivalent ratio of bending R3e, is obtained asfollows:

$R_{3,e} = {\frac{f_{150}^{150}}{MOR}*100}$

As a result, some proposed designs have changed the entry variable ofbending strength (MOR) in the current design of pavements. This seeks toinclude the residual strength that fibers provide when beam tests toconcrete pavements are performed.

Other studies have demonstrated (Altoubat. Et al. 2004) that theincrease in the bending strength of slabs, due to the use of fibers, isdirectly related to the residual strength R3,e.

With this, the proposed method for pavement design to incorporate theeffect of the incorporation of fibers is given by the followingcalibration factor:

${C\; 2^{*}} = \left( {1 + \frac{{Re},3}{100}} \right)$

where:

C2*=Calibration factor of resistance in Equation of fatigue

R3,e=Equivalent ratio of residual strength of 3 mm of deflection in airbeam test.

According to the above equation, one fiber concrete that reaches a ratioof residual strength of 20% will increase by 20% the bending strength ina pavement. With this increase the thickness of the slab can decrease orhave a longer lifetime for a same thickness.

Based on the highest tensile stress in each loading position, theallowed steps for each condition (Nijk) are calculated based on theequation of fatigue:

${\log \left( N_{ijkl} \right)} = {2 \times \left( \frac{C_{3} \times \sigma_{ijkl}}{{MOR} \times C_{1} \times C_{2}} \right)^{{- 1},22}}$(Covarrubias  2008)

where the variables are defined as follows:

Nijkl=Passes permitted for the axle in position k,ç; warp i(temperature), load level j, and critical stress on the top and bottom.

σijkl=Principal stresses calculated using ISLAB2000 for axle in positionk,ç; warp i (temperature), load level j, and critical stress on the topand bottom.

MOR=Flexural strength of concrete after 90 days.

C1=Correction factor for the slab geometry and thickness.

C2=Structural correction factor of fiber.

C3=Load correction factor at the edge.

Using Miner's hypothesis, the fatigue damage for each position isdetermined at the top and bottom of the slab on the basis of thefollowing formula:

${FD}_{k} = {\sum\limits_{i}\; \frac{n_{ijk}}{N_{ijk}}}$

where:

FD=Fatigue damage for a given position of the axle k.

nijk=Number of passes for the local stress I for condition i, j, k.

Nijk=Number of allowed passes for the local stress I for condition i, j,k.

In the document JP2004224633, a pretensioned concrete slab is described,which is easily manufactured and reduces losses due to pre-stress.Pretensioned concrete slab consists of a cured body, which compositionincludes 100 parts of mass of cement, 10-40 parts of particles of finemass, 15-55 parts of particles of inorganic mass, an agent which reducesthe water, and water. The composition may further contain fineaggregates of particles of less than or equal to 2 mm in diameter andone or more types of fibers selected from the group consisting of metalfibers, organic fibers and carbon fibers.

The document CN101823860 describes concrete slabs with powdered fibers,comprising the following components in proportions by weight: 35-40% ofquartz powder, 30-35% cement, 6% fiber and 24 to 29% of reactionassistants, wherein the fibers are vegetable fibers and/or glass fibersresistant to alkalis, and the reaction comprises a 23 to 28% of mineralassistant and 1% of chemical assistant. With the mixture slab ofconcrete with powdered, active and high toughness fibers is obtained,which has the advantage of being lightweight.

On the other hand, the document CN101294430 describes autoclave-aeratedconcrete slab containing carbon fibers.

The document WO0212630 describes a system and method for constructinglarge and continuous concrete slabs, without using conventional controljoints for contraction. The base of the system is formed by a network ofinducing cracks, on which the concrete is poured in such a way that thenetwork is covered by the concrete. The inductors will allow cracking atthe slab once the concrete slab is being used.

The national register CL 44.820 describes a method for constructing slabof concrete and the concrete slab formed comprising the construction ofslab of concrete whose maximum length is 3 meters and its maximum widthis equal to half the width of the track. The formed concrete slab has asize such that one single wheel, or a single set of gear wheels of avehicle, will be always touching and resting on the slab.

Among the documents of the state of the art, there are documentsdescribing concrete slabs with different types of fibers, but said slabsare not intended for use in pavements of low traffic roads. Therefore,it would be desirable to have a slab of concrete to be used in lowtraffic roads on existing ground, which is easy to manufacture, withinstallation and craftsmanship and durability lower costs.

Therefore, an object of the present invention is to provide a slab ofconcrete with structural fiber, to be installed on low-traffic roads.Another objective is to provide a method of manufacturing a concreteslab in situ on low traffic roads and a method for paving roads of lowtraffic, with a concrete mixture, which in this case carries structuralfiber.

Abstract of the Invention

The present invention relates to a method for paving roads with lowtraffic, with a slab of concrete, optimized with fiber, to the concreteslab with obtained fiber, and the method for obtaining the concrete withfiber slab.

BRIEF DESCRIPTION OF FIGURES

The present invention will be described below with reference to thedrawings, which are included to provide a further understanding of theinvention.

FIG. 1 is a diagram of a heavy truck, showing the relevant dimension D1,to be considered in the present invention.

FIG. 2 is a diagram of a heavy truck, showing the relevant dimension D2,to be considered in the present invention.

FIG. 3 is a diagram of a heavy truck, showing the relevant dimension L,to be considered in the present invention.

FIG. 4 is a schematic top view of the maximum size that a slab ofconcrete of the present invention should have.

FIG. 5 is another schematic top view of the maximum size that a slab ofconcrete of the present invention should have, in relation to a standardhaulage truck with a wheel train.

FIG. 6 corresponds to a graph illustrating the strength of concretethrough the deformation of the slab as a function of load.

FIG. 7 corresponds to a graph showing an example of the expected trafficfor different thicknesses.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for manufacturing a fiberconcrete slab for paving low traffic roads or paths, wherein a lowtraffic road comprises a circulation of no more than 50 trucks per day.

This invention greatly reduces the cost of low traffic roads, making itcompetitive with the cheapest existing solutions, even with low trafficasphalt pavements. Furthermore, with respect to the latter, the durationwill be higher, because the concrete has no significant damage due toenvironmental agents and fiber. In the case of cracking, it will extendits lifespan even further, making it not only an economic pavement inits initial cost, but also in the design stage.

A table comparing the initial costs of possible concrete structures isdescribed below:

Transit (EE) H° Trad TCP UTCP 50.000 $170.540 $158.750 $150.920 100.000$179.067 $169.700 $162.260 150.000 $187.594 $180.650 $173.600 250.000$204.648 $191.600 $184.940

Where “H° Trad” refers to concrete designed by traditional methods,“TCP” refers to concrete protected in the record CL 44,820, and “UTCP”represents the fiber concrete of the present invention.

Furthermore, the present invention relates to fiber concrete slab havinga predetermined width and length, depending on the mechanical stressesgenerated by a standard haulage truck that has a free distance betweenthe front wheels and a track width of a train rear wheels and a lengthof free distance between the front axle and the rear axle of the trainwheels, and about of 5 to 15 cm thick. The present invention used as areference medium, the support points of a standard haulage truck,generated by the four points of support of its wheels, bearing in mindthat a standard haulage truck is typically equipped with two frontwheels and two pairs of rear wheels (rear wheels train). For purposes ofdescribing the dimensions of width and length of the fiber concreteslab, the variables D1, D2 and L (FIG. 1) are defined in a standardhaulage truck. Thus, the front wheels of a standard haulage truck willbe separated at a free distance D1 and the wheels on the rear wheeltrain shall be spaced at a free distance D2. At the same time, the freedistance between the front axle and the rear axle, is L.

The concrete slab comprises a dose of between 1 kg/m3 (kg of fiber percubic meter of concrete) and 6 kg/m3 for plastic fibers and between 15kg/m3 (kg of fiber per cubic meter of concrete) and 40 kg/m 3 ofstructural metallic fiber. These doses, of such fibers or other to beused should be such that should generate a residual strength of 10% to50% of the maximum strength of the concrete. The possible fibers to beadded to the mixture are fibers of steel, glass, polypropylene or carbonor some other type of structural fiber for concrete and these fibers canbe added independently or based on mixtures of the same. The thicknessof the slab is approximately between 5 to 15 cm. The minimum dimensionsof the width and length of the slab must be higher than 50 cm and themaximum dimensions of width and length of the slab should be less than2.5 meters. The dimensions of width and length of the slab always allowone wheel, or one wheel train of said standard haulage truck, to besupported and resting on the slab.

In order to ensure that always only one wheel or one set of wheels ofthe standard haulage truck is touching and resting on the slab, the slabmust have a maximum width (Dx) that is minor than the lesser value offree distance between D1 and D2, and a maximum length (Lx) that is minorthan the free distance L. Thus, the fiber concrete slab will have amaximum width Dx and a maximum length Lx, thus ensuring that only onewheel or one set of wheels, rests on the slab when the truck passes bythe road or highway.

However, in a practical form, paving sections can be further enlargedthan the dimensions Dx and Lx, and once manufactured they can be cutaccording to the dimensions Dx and Lx, allowing natural cracking byretraction of the concrete in addition with loads traffic, they producethese dimensions by cracking of the slab, or inducing the cracking withmechanical devices. This, in such a way to make the cuts or cracking ofthe pavement slabs to distances that will generate slab dimensions thatchange the effect of the load of the axles of the trucks or vehiclesused as a design reference. In a preferred embodiment of the presentinvention, the cuts are made of less than 2.5 m in the longitudinaldirection and a longitudinal section that decreases the slab width atleast to a dimension equivalent to the half of the track width. In thecase of Chile, the slabs would be ideally of 1.75 meters long and 1.75meters wide. These dimensions are not the only possible, but generate asample that becomes the system more understandable. Currently, thiscutting is typically made at distances between 3 to 6 meters in thetransverse direction, leaving slabs of these lengths in the longitudinaldirection, and the width of the normal track width of 3.5 meters.

The concrete slab will be placed directly on the natural terrain andexcept in the case of not being suitable or not be uniform, areplacement should be generated, as punctual improvement of thesubgrade. Nevertheless, this improvement does not involve adding anyadditional surface. As an example of this improvement, an excerpt of theManual of Highways of Chile, is shown.

“The removal of land unsuitable material is necessary when this does nothave minimum support capabilities provided in 5.201.3 MC-V5. In summary,materials considered improper will be those meeting at least one of thefollowing conditions:

-   -   1. Materials with a bearing capacity minor than 3% CBR, measured        according to the method prescribed in of the MC-V8 8.102.11,        unless this can be compacted in place and achieve an equal or        higher than 3% CBR support.    -   2. Materials containing more than 3% by weight of dried organic        matter at 60° C., this will be determined according to the assay        described in the Manual of Highways V.5, chapter 5,201,303.    -   3. Material which expansion ratio is greater than 3%, according        to the assay 8.102.11 of the MC-V8.”

The minimum value of the width Dx is higher than 50 cm, andalternatively, the maximum dimension of the width is equivalent to halfof the normal track. Similarly, the minimum value of the length Lx ishigher than 50 cm and the maximum length may correspond to 3.0 meters,depending on the distance between axles of the truck in reference.

The manufacturing method of the fiber concrete slab comprises:

a) determining the width of the slab (Dx) in a free distance Dx, whichis smaller than the lowest value between D1 and D2;

b) determining the length of the slab in a free distance Lx, smallerthan the value of the length L of free distance between the front axleand the first rear axle of the wheels train of the standard haulagetruck;

c) establishing the slab thickness, according to the amount of traffic,traffic loads, the bearing capacity of the natural ground, the concretestrength, the residual strength of concrete and climate; such that thethickness is within the range of 5 to 15 cm;

d) determining the amount of fiber required for a required designresidual strength of between 10% and 50% of the maximum strength of theconcrete; and preparing the mixture of concrete, adding the fiber doseof between 1kg/m3 and 6kg/m3 for fibers of plastic, and of between 15kg/m3 and 40 kg/m3 of metal fiber, wherein the fiber is selected fromfibers of steel, glass, polypropylene or carbon; and

e) pouring the concrete mixture with fiber directly on the road or pathto be paved.

Meanwhile, the method for paving low traffic roads comprises:

a) providing for paving a road or path which have neither asphalt orconcrete paving;

b) evening out and leveling the road or path to be paved;

c) determining the width of the slab (Dx) in a free distance Dx, whichis smaller than the lowest value between D1 and D2;

d) determining the length of the slab in a free distance Lx, smallerthan the value of the length L of free distance between the front axleand the first rear axle of the train wheels of the standard haulagetruck;

e) establishing the slab thickness, according to the amount of traffic,traffic loads, the bearing capacity of the natural ground, the concretestrength, the residual strength of concrete, and climate; such that thethickness is within the range of 5 to 15 cm;

f) determining the amount of fiber required for a required designresidual strength of between 10% and 50% of the maximum strength of theconcrete; and preparing the mixture of concrete by adding the fiber indose of between 1 kg/m3 and 6 kg/m3, for plastic fibers and between 15kg/m3 and 40 kg/m3 of metallic fibers, where the fiber is selected fromfibers of steel, glass, polypropylene or carbon; and

g) pouring the concrete mixture with fiber directly on the road or pathto be paved of the step a), in a size of a paving section greater to themeasures identified in c) and d), and dimensioning the paved section tothe measures determined in steps c) and d); or

h) pouring the concrete mixture with fiber directly on the road or pathto be paved of the step a) in a paving section which has the measuresdetermined in steps c) and d).

The slab of the present invention is only to pave roads that do not haveasphalt or concrete paving roads or paths and does not include therenovations of old pavements with concrete bonded overlays. Furthermore,the slabs of the present invention can be placed on any terrainartificially stabilized.

The evening out and leveling of the road to be paved comprises theremoval of not suitable material that might be on the same.

In addition, the slabs of the present invention can be manufactured inlarger sizes than the measures Lx Dx, and could not be cut to sizeestablished by the Dx and Lx measures, such that the road can be pavedwith slabs of larger sizes than Dx and Lx measures. In this case, whendriving vehicles on the road, due to the weight of vehicles, cracks willbe produced, leaving by this way, slabs which sizes are such thatwhenever a single wheel or single wheel train of the standard haulagetruck is always supported by the paving slab, touching same.

The slabs of the invention have the particular feature of not requiringany armor, mesh, load transfer bars, tie bars, pins or lateralstructural basis in its construction.

The slabs of the present invention, by having structural fiber presentan increased resistance to fatigue, increased load transfer and slabstie to prevent separation or to control soil erosion.

FIG. 5 corresponds to an example of the present invention and shows agraph which illustrates the minimum expected traffic of the pavementslabs of the present invention to various slab thicknesses. Each curvein the graph represents the values obtained for different thicknesses ofthe slabs. Curves, identified from the lower to the upper curvecorrespond to 9 cm, 10 cm, 11 cm, 12 cm and 13 cm of slab thickness,respectively. The graph represents the characteristic flexural strengthat 28 days, with 20% of fiber, the value of HF 4.5 at 28 days.

In the X axis of the graph, the value of CBR (California Bearing Ratio)or relative support value of ground is shown, which states in a directform, a measure of cracking strength.

As an example the following profiles type are shown:

Notes:

-   -   It is considered as a criterion of failure a 50% of slabs with a        crack, due to the presence of fiber and low traffic for which        this solution was designed, the expected real traffic is higher        than shown in the graph.    -   The average thickness of the section it is considered, so in the        case of making a trapezoidal profile it is recommended to reduce        the center of the road in 1 cm and increase the edge by 2 cm.        This will decrease the edge effect so the pavement will last        longer than shown in the graph.    -   This table is only a reference; the pavement should be designed        with OptiPave or with an Abaco specific in design.

1. Method for paving low-traffic roads or paths with a paving slab thatis cast in situ, where the said slab has a width Dx narrower than thesmaller value of D1 and D2, being D1 the free distance between the frontwheels of a standard haulage truck, and D2 is the free distanceseparating the wheels of the rear-wheel train, and a length of thepaving slab Lx that is shorter than the value of the length L of thefree distance between the front axle and the first rear axle of thewheel train of the standard haulage truck, such that the dimensions Dxand Lx mean that a single wheel or, alternatively, a single wheel trainof the standard truck is always supported by the paving slab, touchingsame, CHARACTERIZED in that said method comprises: a) providing forpaving either a low-traffic road which has neither asphalt or concretepaving, or a low-traffic path; b) evening out and leveling the road orpath to be paved; c) determining the width of the paving slab Dx; d)determining the length of the paving slab in a free distance Lx; e)establishing the thickness thereof in accordance with the amount oftraffic and the traffic load, the bearing capacity of the naturalground, the strength of the concrete, the residual strength thereof andthe climate, such that the thickness is between 5 and 15 cm; f)determining the dose of fiber so that the required design strengthresidual is from 10% to 50% of the maximum strength of the concrete andpreparing the concrete mixture by adding fiber, being selected fromsteel, glass, carbon or polypropylene fibers or some other type ofstructural fiber for concrete; and if the fibers are plastic fibers, themixture contains from 1 kg/m3 to 6 kg/m3 (kilograms of fiber per cubicmeter of fiber concrete), and if the fibers are metallic fibers, themixture contains between 15 kg/m3 to 40 kg/m3; and g) pouring theconcrete mixture with fiber directly on the road or path to be paved ofthe step a) in a paving section of larger size than the measuresidentified in c) and d), and measuring the paved section to certainmeasures in steps c) and d); or h) pouring the mixture of fiber concretedirectly on the road or path to be paved in step a), in a paving sectionwhich has the measures determined in steps c) and d).
 2. Method forpaving low-traffic roads and paths with a paving slab, according toclaim 1, CHARACTERIZED in that a low traffic path comprises a trafficflow of no more than 50 trucks per day.
 3. Method for paving low-trafficroads and paths with a paving slab, according to claim 1, CHARACTERIZEDin that the minimum value of Dx is greater than 50 cm and the maximumdimension of Dx is equivalent to half the width of the track.
 4. Methodfor paving low-traffic roads and paths with a paving slab, according toclaim 1, CHARACTERIZED in that the minimum value of Lx is greater than50 cm and the maximum dimension of Lx corresponds to 3.0 meters. 5.Concrete slab for paving low-traffic roads or paths and has a width Dxnarrower than the smaller value of D1 and D2, being D1 the free distancebetween the front wheels of a standard haulage truck and D2 is the freedistance separating the wheels of the rear-wheel train; and a length ofthe paving slab Lx that is shorter than the value of the length L of thefree distance between the front axle and the first rear axle of thewheel train of the standard haulage truck, such that the dimensions Dxand Lx mean that a single wheel or, alternatively, a single wheel trainof the standard truck is always supported by the paving slab, touchingsame, CHARACTERIZED in that said slab comprises a mixture of concreteand fiber, being the fibers selected from steel, glass, polypropylene,carbon fibers or some other type of structural fiber for concrete,because if the fibers are plastic fibers, the mixture contains from 1kg/m3 to 6 kg/m3 (kg of fiber per cubic meter of concrete), and if thefibers are metal fibers, the mixture contains between 15 kg/m3 to 40kg/m3; and in that the slab thickness is within the range of 5 to 15 cmand the amount of fiber to be added to the mixture should be such thatthe slab has a residual resistance from 10% to 50% of the maximumstrength of the concrete.
 6. Paving slab for paving low-traffic roads orpaths according to claim 5, CHARACTERIZED in that the minimum value ofDx is higher than 50 cm and the maximum dimension of Dx is equivalent tohalf the width of the track.
 7. Paving slab for paving low-traffic roadsor paths according to claim 5, CHARACTERIZED in that the minimum valueof Lx is greater than 50 cm and the maximum dimension of Lx correspondsto 3.0 meters.
 8. Paving slab for paving low-traffic roads or pathsaccording to claim 5, CHARACTERIZED in that the mentioned concrete slabis suitable for low-traffic roads comprising a circulation of no morethan 50 trucks per day.
 9. Manufacturing method of the concrete slab ofclaim 5, which comprises producing a paving slab to be poured in situ,where the said paving slab has a width Dx narrower than the smallervalue of D1 and D2, being D1 the free distance between the front wheelsof a standard haulage truck and D2 is the free distance separating thewheels of the rear-wheel train; and a length of the paving slab Lx thatis shorter than the value of the length L of the free distance betweenthe front axle and the first rear axle of the wheel train of thestandard haulage truck, such that the dimensions Dx and Lx mean that asingle wheel or, alternatively, a single wheel train of the standardtruck is always supported by the paving slab, touching same,CHARACTERIZED in that said method comprises: a) determining the width ofthe slab (Dx) in a free distance Dx,; b) determining the length of theslab in a free distance Lx; c) establishing the thickness of the slab,according to the amount of traffic, traffic loads, the bearing capacityof the natural ground, the strength of concrete, the residual strengthof concrete and climate; such that the thickness is within the range of5 to 15 cm; d) determining the amount of fiber required for a requireddesign residual strength of between 10% and 50% of the maximum strengthof the concrete; and preparing the concrete mixture by adding fiber,being selected from steel, glass, polypropylene, carbon fibers or someother type of structural fiber for concrete; and if the fibers areplastic fibers, the mixture contains from 1 kg/m3 to 6 kg/m3 (kilogramsof fiber per cubic meter of fiber concrete), and if the fibers are metalfibers, the mixture contains between 15 kg/m3 to 40 kg/m3; and e)pouring the concrete mixture with fiber directly on the low-traffic roador path to be paved.
 10. Method for manufacturing a concrete slab, inaccordance with claim 9, CHARACTERIZED in that a low traffic roadcomprises a circulation of no more than 50 trucks per day.